Improving the understanding and management of skin set, bloom and netting in potatoes

Manipulation of skin set 

With Cara, there were effects of N on skin set in 2002 only, when senescence at haulm destruction was about 30%, compared with 55% in 2001 and 46% in 2003. So over-application of N had a negative effect on skin set if the crop was defoliated at early canopy senescence. Chitting and planting date did not affect skin set, but did affect canopy senescence, showing that skin set at harvest cannot be predicted solely by senescence at defoliation. There were differences between cultivars in skin set and growers therefore need to take care with N application rates for varieties known to suffer from poor skin set.

Un-setting of skins 

Skin unsetting was found to occur within two hours after harvest. The effects of several factors were examined, including haulm destruction method, post-harvest tuber environment and handling. The tuber environment (in particular excess moisture pre- and post-haulm destruction), and small impacts when handling the crop, were shown to exacerbate unsetting.

Skin bloom and black dot 

Field treatment factors included seed maturity, planting date and harvest date and these produced differing skin bloom characteristics. Storage treatments were imposed to study effects of store environment on maintenance of bloom.

Crop duration was shown to affect skin quality: longer duration crops tended to have more black dot and have duller skins (i.e. less bloom) after prolonged storage. An immediate temperature pull-down following harvest consistently minimised black dot development and skin bloom deterioration. Poor skin bloom was shown to result from a loss of integrity of the periderm surface.